The present invention relates to measurement of flow of a process fluid in an industrial process. More specifically, the present invention relates to a flow transmitter.
Flow rate measurement derived from differential pressure measurements is common in the art and is found in many types of fluid flow meters. Pitot tubes, for instance, sense the upstream (or “stagnation”) pressure of a flowing fluid and a downstream (including “static” or “suction”) pressure to produce a differential pressure value that is related to the rate of flow of the fluid that is impacting the pitot tube. An averaging pitot tube includes pressure ports leading to fluid plenums in the pitot tube body. Impulse lines then transmit the fluid pressures to a flow calculating device, such as an industrial process variable transmitter.
The process variable transmitter includes at least one sensor which receives the differential pressure. For example, a differential pressure sensor can be used which receives upstream and downstream pressures from a pitot tube type bluff body and responsively provides an electrical output related to a pressure difference between the two pressures. Circuitry within the transmitter is configured to responsively calculate flow based upon the sensed differential pressures.
The functionality of the existing flow meter consisting of an averaging pitot tube and differential pressure sensor is proven and valued in many applications. However increased functionality is possible with the measurement of multiple pressures. Further, additional measurements would enable diagnostics such as clogging of plenums, pipe blockage, installation problems, sensor failures, etc.